This work involves the development of a new facile procedure for isolation of cell surface proteins as well as facile methods for identifying proteins unique to the surface of transformed cells. Purification of such unique proteins and administration to an individual animal could activate the immune response enabling tumor rejection. Our proposed procedure for the isolation of cell surface protein involves synthesis of macromolecular reagents consisting of a) a reactive group capable of forming a specific covalent bond with proteins; b) a macromolecular carrier, and c) a linkage between the two that is stable under normal physiological conditions, but may be selectively broken. The reactive group can be designed with many variations in specificity. Reagents directed toward thiol groups, amino groups and reagents directed toward serine proteinases on the surface of cells are being studied at this time. The advantages of the methods using the solid phase reagents include high yield of selected protein, ability to wash away solubilizing agents, minimal contact with degradative enzymes, minimal manipulation, and the possibility of regenerating native protein. Proteins released from the resin will be further purified by electrophoresis and ion exchange chromatography. Purified proteins characteristic of transformed Balb/c 3T3 cells will be tested in Balb/c mice for the ability to enhance tumor rejection.